Role of diquark correlations and the pion cloud in nucleon elastic form factors

Abstract

Electromagnetic form factors of the nucleon in the space-like region are investigated within the framework of a covariant and confining Nambu-Jona-Lasinio model. The bound state amplitude of the nucleon is obtained as the solution of a relativistic Faddeev equation, where diquark correlations appear naturally as a consequence of the strong coupling in the colour $\bar{3}$ $qq$ channel. Pion degrees of freedom are included as a perturbation to the "quark-core" contribution obtained using the Poincaré covariant Faddeev amplitude. While no model parameters are fit to form factor data, excellent agreement is obtained with the empirical nucleon form factors (including the magnetic moments and radii) where pion loop corrections play a critical role for $Q^2\lesssim 1$GeV${}^2$. Using charge symmetry, the nucleon form factors can be expressed as proton quark sector form factors. The latter are studied in detail, leading, for example, to the conclusion that the $d$-quark sector of the Dirac form factor is much softer than the $u$-quark sector, a consequence of the dominance of scalar diquark correlations in the proton wave function. On the other hand, for the proton quark sector Pauli form factors we find that the effect of the pion cloud and axialvector diquark correlations overcomes the effect of scalar diquark dominance, leading to a larger $d$-quark anomalous magnetic moment and a form factor in the $u$-quark sector that is slightly softer than in the $d$-quark sector.

30 pages and 40 figures

References in corpus (17)

• High-precision determination of the electric and magnetic form factors of the proton
• Determination of the Charged Pion Form Factor at Q2=1.60 and 2.45 (GeV/c)2
• Flavor decomposition of the elastic nucleon electromagnetic form factors
• Measurements of the Electric Form Factor of the Neutron up to Q2=3.4 GeV2 using the Reaction He3(e,e'n)pp
• Charged pion form factor between $Q^2$=0.60 and 2.45 GeV${}^2$. I. Measurements of the cross section for the ${}^1$H($e,e^{\prime }{\pi }^{+}$)$n$ reaction
• Measurement of Strange Quark Contributions to the Vector Form Factors of the Proton at Q**2=0.22 (GeV/c)**2
• Masses of ground and excited-state hadrons
• Interplay of Spin and Orbital Angular Momentum in the Proton
• Transversity quark distributions in a covariant quark-diquark model
• Electromagnetic structure of the lowest-lying decuplet resonances in covariant chiral perturbation theory
• Resolution of the Proton Spin Problem
• Chiral extrapolation of nucleon magnetic form factors
• The NJL-jet model for quark fragmentation functions
• Calculating Kaon Fragmentation Functions from NJL-Jet Model
• Third Zemach Moment of the Proton
• Collins Fragmentation Function within NJL-jet Model
• Manifestly-covariant chiral PT calculation of nucleon Compton scattering

Cited by in corpus (20)

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• Dressed Quark Mass Dependence of Pion and Kaon Form Factors
• SU(3)-flavour breaking in octet baryon masses and axial couplings
• Genuine empirical pressure within the proton
• Quark spin and orbital angular momentum from proton GPDs
• Generalized parton distributions in spin-3/2 particles
• Nuclear medium meson structures from the Schwinger proper-time Nambu--Jona-Lasinio model
• Properties of neutral mesons in a hot and magnetized quark matter: size-dependent effects
• An Improved Hadronic Model for Pion Electroproduction
• Regularization dependence of pion generalised parton distributions
• Electroweak properties of kaons in a nuclear medium
• Inverse magnetic catalysis and size-dependent effects on the chiral symmetry restoration
• Intrinsic Glue and Wilson lines within Dressed Quarks
• Medium effects on the electromagnetic form factors of the $\rho$ meson
• The kaon off-shell generalized parton distributions and transverse momentum dependent parton distributions
• Isospin breaking from diquark clustering
• Gluon EMC effects in nuclear matter